I think it very much depends on the population. Online quiz takers will skew young, whose English is a lot better than that of middle aged and older Swedes, on average. Most Swedes I know have at least competency in English, and I know a lot of them, from being in Sweden too, but I'm sure my sample is also biased. Nonetheless, I'm not suprised at the fluency of Swedes in foreign langauges compared with other countries. As with the Netherlands, they are not an inward-looking culture particularly.